194 /• /• Christian 



The amount of cortical stroma may vary considerably; it is inconspicuous 

 in most rodents whereas it is marked in most carnivores. 



b. Zonation of the adrenal cortex. Three distinct major zones usually are 

 identifiable histologically in the cortex, although the zonation is difficult to 

 discern in a number of species (Bourne, 1949) . An outer thin zona glomeru- 

 losa lies just beneath the capsule and consists of loops or balls of rather 

 large cells with relatively clear cytoplasm. Central to the zona glomerulosa 

 is a wide central zona fasciculata, which is composed of radially arranged 

 straight cords of polyhedral cells that usually contain numerous cytoplasmic 

 lipid vacuoles. Lipid vacuoles occur in the cortical cells of most species, 

 but they may be absent in some, for example, the golden hamster (il/c.so- 

 cricetus auratus) (Alpert, 1950; Knigge, 1954a; Schindler and Knigge, 

 1959a). Little or no lipid is present in the cortices of cattle, sheep, and 

 pigs (Deane and Seligman, 1953). When present, the vacuoles may vary 

 considerably in size and number, depending on variations in the activity 

 of the cortex. The cells of the outer half of the zona fasciculata usually are 

 larger and contain more lipid than those in the inner half of the zone. The 

 fascicular cords are arranged as paired columns of cells lining vascular 

 sinusoids in man and monkeys (Elias and Pauly, 1956), but is continuous 

 in rats, the sinusoids penetrating the continuum (Pauly, 1957). The latter 

 normally contain large amounts of blood circulating from the arteries in 

 the capsule to the medullary venous sinusoids and adrenal vein. There are 

 variations in the circulatory arrangement with species, and it is more com- 

 plex in detail than has been described here, but these matters are thoroughly 

 covered elsewhere (Gersh and Grollman, 1941; Hartman andBrownell, 

 1949; Harrison, 1951, 1957; Elias and Pauly, 1956; Pauly, 1957). The cells 

 of the fasciculata, when stamed by routine procedures, bear a marked 

 resemblance to the luteal cells of the ovary, interstitial cells of the testis, 

 and, although less closely, the cells of the "brown fat" or "hibernating 

 gland" in its usual functional state. The zona reticularis forms a fairly wide 

 cortical band between the medulla and the zona fasciculata in most species, 

 but it is not always present (Hartman and Brownell, 1949). Its cords (or 

 cortical continuum) are more or less continuous peripherally with those of 

 the zona fasciculata, but they rapidly break up into a reticular network as 

 they proceed centrally toward the medulla. The cells are generally smaller 

 than other cortical cells and usually contain no vacuoles. However, when 

 vacuoles are present, they are usually very large. 



There is need for a detailed, well illustrated, and thorough discussion of 

 the comparative morphology of the adrenal glands which would include a 

 wide variety of species and a sufficient number of animals of each species 

 to describe age and sex, as well as seasonal and environmental, relation- 

 ships. It is not the purpose of the present discussion to dwell on the anatomy 



